The present invention relates to a magnetic head, and more particularly to an improved magnetic head for use in flexible magnetic disk devices.
In general, in magnetic disk devices, especially flexible magnetic disk devices, there has been extensively employed a magnetic head of layered structure which includes a write/read layer for writing and reading data and which is provided on both the sides of the write/read layer with erase layers for erasing the edge portions of newly written data in a writing operation and previously written data. There has also been an erase structure of the tunnel type in which the gaps of the erase layers are shifted and arranged backward in the traveling direction of a disk medium with respect to the gap of the write/read layer.
In such erasing magnetic head of the tunnel type, it is desirable that magnetic core portions forming the erasing magnetic flux paths in the two erase layers on both the sides of the write/read layer be put into completely closed forms so as to suppress the leakage of erasing magnetic fluxes into the write/read layer, thereby to enhance the efficiencies of the erase layers. Especially in the presence of leakage of the erasing magnetic flux into the write/read layer in the writing operation, there have been serious problems concerning the performance of the magnetic head, such as the occurrence of an erasing bias action which distorts a signal waveform.
A prior-art magnetic head therefore comprises a write/read layer 1 consisting of a nonmagnetic material 3 and a magnetic material 4, and erase layers 2 consisting of a nonmagnetic material 5 and a magnetic material 6, as shown in FIG. 1. Nonmagnetic sliders 11 are bonded on both the sides of the erase layers 2. A write/read coil 7 is wound round the magnetic material 4, and a write/read-back core 8 is mounted thereon. Further, an erase coil 9 and erase-back cores 10 are mounted on the magnetic material 6, 6. By installing the erase-back cores 10, the erasing magnetic flux paths are closed to prevent the aforementioned leakage of the erasing magnetic fluxes.
Since, however, such erase-back core 10 in the prior art is a flat plate and does not have a holding portion, it needs to be pressed (tentatively fixed) with a jig or by hand during installation, and the assemblage takes a long time. Besides, the installation of the erase-back core 10 sometimes incurs the trouble that a part of the erase layer or the write/read layer is damaged. Further, since a resin for the tentative fixation is liable to enter the joint plane between the erase-back core 10 and the magnetic material 6, the characteristics of the core are apt to disperse. In addition, an oxide magnetic material such as ferrite is used as the material of the erase-back core 10. When fabricating the erase-back core 10 out of ferrite, this material needs to be mirror-finished to prevent a backward gap being formed in the joint plane between the magnetic material 6 and the erase-back core 10. This also leads to the problem that the erase-back core becomes costly.